Effect of Surface Charge on the Fabrication of Hierarchical Mn-Based Prussian Blue Analogue for Capacitive Desalination.

Multiple and hierarchical manganese (Mn)-based Prussian blue analogues obtained on different substrates are successfully prepared using a universal, facile, and simple strategy. Different functional groups and surface charge distributions on carbon cloth have significant effects on the morphologies and nanostructures of Mn-based Prussian blue analogues, thereby indirectly affecting their physicochemical properties. Combined with the advantages of the modified carbon cloth and the nanostructured Mn-based Prussian blue analogues, the composite with negative surface charge formed by the electronegativity differences shows good electrochemical properties, leading to improvement in charge efficiency during capacitive desalination. An asymmetric device fabricated with Mn-based Prussian blue analogue-modified F-doped carbon cloth as the cathode and acid-treated carbon cloth as the anode presents the highest salt adsorption capacity of 10.92 mg g with a charge efficiency of 82.28% and the lowest energy consumption of 0.45 kW h m at 1 V due to the main influencing factor from the negative surface charge leading to co-ion expulsion boosting the capacitive deionization performance. We provide insights for further exploration of the relationship between second-phase materials and carbon cloth, while offering some guidance for the design and preparation of electrodes for desalination and beyond.